The present invention relates to a sample transfer vessel and, in particular, relates to such a vessel adapted to interface with an ultra-high vacuum system.
In recent years several new techniques for determining the elemental and chemical nature of sample surfaces have been developed. A number of the more sophisticated techniques are performed in an ultra-high vacuum environment. One such technique is commonly known as ESCA (electron spectroscopy for chemical analysis) wherein the surface of a sample is bombarded with soft X-rays which liberate photoelectrons from the sample surface. All elements, with the exception of hydrogen, within the bombarded volumes which are present in detectable amounts generate well-defined peaks in the photodetection energy distribution. The elemental composition of the surface is then determined from the energy positions of the peaks in the spectrum. The ESCA technique provides quite accurate information and, because of the degree of accuracy, it is imperative that the surface under analysis be free from any form of contamination.
A sample is susceptible to contamination from the moment it is isolated at its source until it is the ultra-high vacuum environment of the analytical instrument. Ideally, the sample is isolated in close physical proximity with the instrument. However, such physical proximity is rarely available in the practical world. This condition exists for a number of obvious reasons, not the least of which is the expense of the instrument itself. Consequently, samples isolated must usually be transported over substantial distances and time to the site of an instrument where the sample is to undergo analysis.
A generally accepted precaution useful only when handling samples which are quite inactive is to isolate and package the sample in a "glove-box". By using such a device, the sample can even be isolated and packaged in an inert atmosphere. When the sample is removed from the package and inserted into the instrument for anslysis, the entire test chamber is required to be evacuated to the desired level. Such a procedure not only is time consuming but also exposes the sample to a potentially contaminating atmosphere until an ultra-high vacuum is achieved. However, such a precautionary procedure is quite unacceptable where the sample is a chemically active material which can be contaminated by the least exposure to an environment other than an inert or ultra-high vacuum ambient.
From the above discussion, it is clear that there is a dire need for a sample transfer vessel within which a sample can be transported and loaded into an instrument without contamination thereof, regardless of the potential for chemical activity of the sample.